So right now I'm working on a DMG calculator for mobs who possess armor.
It's pretty easy to use it, just put in your wep's stats and the level of the enemy you're willing to shoot at. On the next page you can examine the damage for the enemies who are included. All of the formulas are from the wiki, it's pretty accurate still not perfect. Alloy armor still needs testings, corrosive projection is just experimental, more enemies will be added and so on.
Feel free to upload it to your own google drive and use it. I'll make it available w/o google drive by the time it's finalized.